1. Field of the Invention
This invention relates to combustion chamber liners for use in apparatus such as a gas turbine engine, and more particularly, to a combustion chamber liner having an internally cooled labyrinth assembly.
2. Description of the Prior Art
A cross-reference is made to U.S. patent application Ser. No. 07/082,808 filed on Aug. 6, 1987 now allowed, assigned to the same assignee as herein and entitled "Combustion Chamber Liner Having Failure Activated Cooling and Detection System" by the same applicant as herein.
Combustion apparatus or combustors are used in various applications to produce heat or burn a fuel in a controlled environment. One particular use of combustors has been in the area of gas turbine engines. As employed in a gas turbine engine, a combustor ordinarily includes an exterior housing and an interior combustion chamber. Fuel is burned in the interior of the combustion chamber producing a hot gas usually at an intensely high temperature such as 3,000.degree. F. or even higher. To prevent this intense heat from damaging the combustor before it exits to a turbine, a heat shield or combustion chamber liner is provided in the interior of the combustion chamber. This combustion chamber liner thus prevents the intense combustion heat from damaging the combustor or surrounding engine.
In the past, various types of combustion chamber liners have been suggested and used. In addition, a variety of different methods have been suggested how to cool these liners so as to withstand greater combustion heat or prolong the useable life expectancy of the liner. U.S. Pat. No. 2,548,485 by Lubbock and U.S. Pat. No. 3,918,255 by Holden disclose various types of combustion chamber liners. Other U.S. Patent Nos. that describe cooling of combustion chamber liners include U.S. Pat. No. 4,004,056 by Carroll, U.S. Pat. No. 4,269,032 by Meginnis et al, U.S. Pat. No. 4,302,940 by Meginnis, and U.S. Pat. No. 4,315,406 by Bhanger et al. U.S. Pat. No. 4,064,300 by Bhanger has also described a two sheet laminate being connected by heat conductive portions with a cooling fluid passing between the two sheets.
Also in the past, combustion chamber liners were made of special metal alloys. These metal alloys were manufactured to withstand the intense heat in the combustor and allow for a controlled heat transfer so as not to damage or endanger the surrounding engine. However, the cost of these types of metal alloys was unreasonably high and thus lead to the use of a metal and ceramic combination of materials for liners. The use of a metal and ceramic combination liner greatly reduced manufacturing cost of liners in addition to providing a more efficient heat shield.
A problem arises in using presently available combustion chamber liners that have a combination ceramic and metallic material in that ceramic material is normally brittle whereas metallic material is normally ductile, as a result, thermal gradients or differing thermal expansions between the ceramic and metallic material from the intense heat of the combustion chamber results in a substantial likelihood of a crack or break in the ceramic material. This crack or break in the ceramic material is generally known as a failure and allows heat to escape the combustion chamber resulting in further damage to the combustion chamber liner, the combustor and possibly the entire engine.
A further problem arises in using presently available combustion chamber liners having metallic and ceramic layers in that there are no means available to supply sufficient coolant to provide a directed internal cooling of the liner to prevent a failure from occurring.
A further problem arises in that ceramic and metallic combination combustion chamber liners do not have a suitable means to compensate for the inherently different heat expansion properties of the materials in addition to providing a means for cooling the interior of a combustion chamber liner.